In nursing mothers, breast milk immunoglobulin (IgA) and serum IgG responses were higher in patients receiving the inactivated influenza vaccine (IIV) vs those receiving the live attenuated influenza vaccine (LAIV), suggesting that IIV is preferred for these patients, according to a study published in Vaccine.

Rebecca C. Brady, MD, from the Cincinnati Children’s Hospital Medical Center in Cincinnati, Ohio, and colleagues conducted a randomized, double-blind clinical trial to compare immunogenicity of LAIV vs IIV in women who were currently breastfeeding. A total of 248 women aged 18 to 49 years and who had delivered a healthy infant at ≥36 weeks’ gestation were enrolled in the study. The study was conducted during the 2012-2013 influenza season; no participant had received an influenza vaccine for that season.

Women were matched 1:1 to receive either LAIV with intramuscular placebo or IIV with intranasal placebo. Participants recorded intensity of adverse events, injection site symptoms, presence of congestion, cold-like symptoms, or nasal bleeding for 7 days following immunization; events experienced by infants were monitored by mothers for 10 days. Breast milk and serum specimens were submitted at both baseline and 28 days post-immunization.  Expressed milk from the women and nasal swab samples from both women and infants were collected at baseline, as well as 2 days and 8 days after influenza immunization.

Continue Reading

Based on the researchers’ previous investigations, “the primary hypothesis was that LAIV would provide superior induction of breast milk IgA antibody responses to influenza as compared to IIV when administered to nursing women.”

Injection site pain was the most frequently recorded adverse event in IIV recipients (56%), while nasal congestion was the most frequently reported adverse event LAIV recipients (45%). Upper respiratory infection was the most frequently reported unsolicited nonserious adverse event in both groups (10.5% of both LAIV and IIV recipients).

Related Articles

No vaccine or influenza virus was found in the samples of breast milk, and no virus was detected in nasal secretions of women who received IIV. On day 2, an infant whose mother received LAIV during the previous influenza season tested positive for an influenza A vaccine strain; by day 8, the infant’s nasal secretions were negative for all influenza viruses. Breast milk IgA response to H1N1 as well as breast milk titers were higher in IIV recipients compared to LAIV recipients.

Results of the study show that breast milk IgG and serum IgG titers as determined by enzyme-linked immunosorbent assay, and serum hemagglutinin inhibition antibody response were higher in lactating women receiving IIV compared with those receiving LAIV.


Brady RC, Jackson LA, Frey SE, et al. Randomized trial comparing the safety and antibody responses to live attenuated versus inactivated influenza vaccine when administered to breastfeeding women [published online June 28, 2018]. Vaccine. doi: 10.1016/j.vaccine.2018.06.036